1. Field of the Invention
The present invention relates to optical waveguides and lens array for collecting laser beams and a laser collecting device incorporating the same.
2. Description of the Related Art
FIG. 14 shows a general construction of a semiconductor laser beam collecting device known as prior art. The semiconductor laser beam (hereafter referred simply as “laser beam”) 2 is emitted from a beam emitting part 12 on an active layer of a semiconductor laser (like a laser diode or the like) and takes the form of an elliptical in the section normal to the direction in which the laser beam 2 travels. The laser beam 2 of the elliptical form has a fast axis direction and a slow axis direction. The longer the elliptical form is distanced from the beam emitting part 12, the larger it becomes. There has been known a semiconductor laser beam collecting device of the type wherein laser beams emitted from a plurality of beam emitting parts which are arranged in a second-order matrix extending in the fast axis direction and in the slow axis direction are collected by optical fibers of a fewer number to reinforce the output of the laser beams.
For example, where the semiconductor lasers are to be employed as a power source for a laser machining apparatus or a laser material processing apparatus, it must be of a high power. The laser beam emitted from a single beam emitting part is weak in power strength. Thus, a group of lenses are used to collect laser beams emitted from a plurality of beam emitting parts thereby to strengthen the output of the laser beams.
Japanese patent publication No. 2000-98191 discloses a semiconductor laser beam collecting device shown in FIG. 14 as prior art. In the publication, it is proposed to collect laser beams to optical fibers thereby to strengthen the beam output power by utilizing a group of lenses and the optical fibers 30 and arranging a collimating lens array 70 extending in the fast axis direction, a collective lens 80 for collecting beams in the fast axis direction and a collective lens 90 for collecting beams in the slow axis direction, in turn within a space from the beam emitting parts 12 to the optical fibers 30.
In order that laser beams emitted from semiconductor laser emitting parts are collected efficiently to optical fibers thereby to strengthen the output power of the laser beams, it is necessary to gain the density of the beams by entering the beams from much more number of the emitting parts into much finer optical fibers and to enter the beams efficiently into the optical fibers by entering the beams into the entrance surfaces of the optical fibers at a smaller incident angle, namely, at an angle as close as the right angle to the entrance surfaces without reflecting the entered laser beams outside.
The laser beams coming from the emitting parts 12 advance as they spread in the fast axis direction as well as in the slow axis direction. For collection of the laser beams which advance as spreading, the lenses used themselves and the arrangement of the same are to be quite highly accurate.
In the semiconductor laser collecting device known heretofore (e.g., from the aforementioned Japanese patent publication No. 2000-981919, the emitting parts are arranged with a relatively wide spacing in the fast axis direction, and correcting the beams in that direction is carried out once they are transformed into parallel beams. On the other hand, the emitting portions are arranged with a relatively narrow spacing in the slow axis direction, which requires that the lenses used be very small in diameter and difficult to arrange. Thus, collecting the beams in the slow axis direction is carried out without transforming the beams into those parallel.
As understood from the foregoing, the prior art device mentioned above involves the following problems to be solved.
Referring to FIGS. 15(A) and 15(B), the spacing between the slow axis beam collective lens array 90 and the emitting parts 12 is short. It is therefore difficult to arrange the fast axis collimation lens array 70 and the slow axis beam collective lens array 90 properly within the short spacing. The optical fibers 30 are caused to be arranged within a short distance from the emitting parts 12. Thus, where the incident angle (θoutx) in the fast axis direction is set small, the number of the laser beams which can be collected in the fast axis direction is made small, so that it cannot be practiced to obtain high power laser beams from a large number of optical fibers for use in laser machining.